1. Field of the Invention
The present invention relates to a magnetic recording-reproducing apparatus for recording information on a magnetic recording medium or reproducing the recorded information.
2. Description of the Related Art
With the demand for miniaturization and a larger memory capacity of information-processing equipment, the hard disk drives are miniaturized and the recording capacities are increased remarkably. For further increase of the recording density, another novel system for recording and reproducing information is expected.
To cancel an adverse effect of heat fluctuation resulting from micronization of a recording bit, a change is expected from the current system of recording one bit on plural magnetic particles to a novel system employing a patterned medium for recording one bit on a single magnetic particle.
The change to the patterned medium causes problems. In particular, the patterned medium should have the magnetic particles arranged in a regular pattern. In an intended square arrangement of 1 Tb/in2 the magnetic particles are arranged at intervals of 25 nm. Such a medium cannot readily be produced. Moreover, the access with a recording head to the respective magnetic particles cannot readily be achieved.
To solve the former problem, in one method, an intended pattern is formed preliminarily on a mold, and the pattern is imprinted onto a medium for the regular arrangement. To solve the latter problem, a method is disclosed in which recording cell groups containing respectively plural magnetic particles are employed for the information recording and tracking, since the formation of a servo-pattern with fine magnetic particles is difficult (Japanese Patent No. 3704105).
In the above methods of preparation and tracking of the magnetic recording medium, a perfect arrangement is assumed without consideration of positional deviation in the arrangement. In particular, whether the medium is prepared by direct imprinting or by lithography by light exposure or electron beam, a perfect pattern cannot readily be formed over the entire of the medium having a diameter of one inch or more.
As described above, a perfect pattern cannot practically be formed on an area having a diameter of as large as one inch. To meet this difficulty, the entire pattern may be formed by joining plural perfect pattern sections. However, discontinuity can occur at the boundary between the joined sections. The discontinuity between the joined sections renders ineffective the preliminary formation of a pattern of servo-information or the regular arrangement for the tracking.
The present invention provides a magnetic recording-reproducing apparatus which enables tracking even when irregularity is caused between the joined sections of the magnetic recording medium.